1. Technical Field of the Invention
The present invention relates to a thermal development apparatus for heating a photosensitive thermal developable recording material having a latent image formed thereon, to thereby visualize the latent image recorded on the image-forming layer on both faces of the photosensitive thermal developable recording material.
2. Description of the Related Art
Heretofore, there is known an image-forming apparatus in which a photographic material is imagewise exposed, then attached to an image-receiving material and heated for thermal development to transfer the developed image onto the image-receiving material, as in JP-A 2000-221654. In the apparatus of JP-A 2000-221654, water is used as the image-forming solvent for transferring the image from the photographic material to the image-receiving material, and therefore the apparatus is provided with a moisture sensor for moisture control therein.
An image-forming apparatus that is referred to as a medical imager is for forming a print of a visible image from the image analyzed by a medical analyzer such as CT, MRI, etc. In the image-forming apparatus of the type, a photosensitive thermal developable recording material having a photothermographic image-forming layer on a support of PET film or the like is used. In this, briefly, such a photosensitive thermal developable recording material is imagewise exposed with light beams that have been modulated in accordance with the image data fed from the image data supply source such as MRI or the like, thereby forming a latent image on it, and then the exposed material is thermally developed in the built-in thermal development unit in the apparatus to give colored hard copies, and this does not require water at all for an image-forming solvent.
FIG. 6 shows an image-forming apparatus equipped with an ordinary thermal development unit such as medical imager.
The image-forming apparatus 300 basically is provided with a recording material supply section 310, an image exposure section 320 and a thermal development section 330 in that order in the conveyance direction of recording material A.
In the recording material supply section 310, one uppermost sheet of recording material is taken out of the magazine 311 with the pickup roller unit 312, and conveyed to the image exposure section 320.
The image exposure section 320 is a section for imagewise exposing the recording material by scanning exposure of light beams, and the image exposure is performed by imagewise scanning using the laser beams L from the exposure unit 321.
The recording material with a latent image recorded thereon in the image exposure section 320 is then conveyed to the thermal development section 330. In the thermal development section 330, the recording material is heated by a heating unit of curved heat plates 331(a, b, c) for thermal development to convert the latent image into a visible image. A number of conveyor rollers 332 are disposed along the inner face of the curved heat plates 331. The edges of these conveyor rollers 332 are rotated with a large rotary disc 333, whereby the recording material is slid, heated and conveyed between the inner face of the curved heat plates 331 and the conveyor rollers 332 along the inner face of the heat plates 331. In this case, the recording material is heated on its one face by the curved heat plates 331.
Thus kept in contact with the heat plates 331, the recording material is thermally developed by the heat of the heat plates 331, and then this is led to the take-out tray 360 via the pre-cooling section 340 and the cooling section 350, and is thus taken out.
In the drawing, 370 is a power/control unit for power supply to the operation units, for light control in the image exposure unit and for control of the conveyance speed through the units.
In the method of recording a latent image on a recoding material through exposure of the material to light beams that are modulated in accordance with the image data fed from an image data supply source such as MRI, the recording material generally has an image-forming layer formed on one face thereof. In the method, therefore, only one face of the material having the image-forming layer is an object for heating relating to the thermal development of the recording material, as shown in the above-mentioned related-art examples. Even in the thermal development section (thermal development apparatus) of the type for double-sided photosensitive films, heating may be performed also on the face of the recording material not having an image-forming layer thereon (by the auxiliary heat source provided on the side of the material not having an image-forming layer thereon) In this case, however, the temperature control is merely for auxiliary heat control of the image-forming layer formed on one face of the material.
On the other hand, in a double-sided photosensitive pick-up method where an object is put between an X-ray tube and a film and a latent image of the object is recorded on the film by the X-ray having passed through the object, a fluorescent intensifying screen is disposed on both faces of the film (however, when the double-sided photosensitive film has a fluorescent sensitizer layer therein, the sheet is not disposed) and the film is housed in a cassette. When exposed to X-ray, the film may form an image thereon by the action of the fluorescent intensifying screen capable of being excited to give fluorescence through exposure to X-ray. Different from the films for the above-mentioned medical imagers such as CT and MRI, the double-sided photo sensitive films are characterized in that they have an image-forming layer formed on both faces of the support thereof.
If those films having an image-forming layer formed on both faces thereof are processed with the ordinary thermal development apparatus where only one face of films is heated, then the heat transfer to non-heated side of the image-forming layer may be delayed. The development delay often causes discoloration of the image-forming layer into brown or the like. In addition, if sufficient heat could not be transferred to the image-forming layer on the non-heated side, then the development will be insufficient and it may cause image density reduction or fluctuation.
Given that situation, a thermal development apparatus capable of uniformly heating both faces of double-sided photosensitive films has been developed.
FIG. 7 shows the thermal development apparatus capable of uniformly heating both faces of double-sided photosensitive films.
In the drawing, 400 is a thermal development apparatus for double-sided photosensitive films; P (P1, P2, P3 . . . ) is a double-sided photosensitive film; 10′ is a cassette; 11 is an openable lid; 20 is a conveyor unit; 21 is a sucker; 22 is a conveyor roller pair; 23 is a conveyor guide; 30 is a thermal development section; 31 is a first heating unit (heat roller); 32 is a built-in heater; 35 is a second heating unit (heat plate); 36 is a surface heater; 40 is a pre-cooling section; 50 is a cooling section; 60 is a conveyor unit; 61 and 62 are take-out roller pairs; 63 is a conveyor guide; and 70 is a tray. 80 is a power/control unit for power supply to the operation units and for conveyance speed control; 90 is a cassette holder section for holding the cassette 10′.
In the thermal development apparatus 400 of FIG. 7, the double-sided photosensitive film P (in the drawing, P is changed to P1, P2, P3, . . . in accordance with the site where the double-sided photosensitive film is put) (recording material) is heated and the latent image recorded on the image-recording layer of the film is thereby visualized. The double-sided photosensitive film P to be processed in the thermal development apparatus 400 has an image-forming layer of a photosensitive material on both of one and the other faces of the support thereof.
The double-sided photosensitive film P1 having a latent image formed on the image-forming layer on both faces thereof is housed in the cassette 10′, and the cassette 10′ with the film therein is inserted into the cassette holder section 90 of the thermal development apparatus 400. When the cassette 10′ is inserted into the cassette holder section 90, then the openable lid 11 of the cassette 10′ is automatically opened, and the double-sided photosensitive film P1 is taken out of the cassette 10′ by a take-up unit with the sucker 21 or the like (it may be a pickup roller).
The thermal development apparatus 400 may be provided with a magazine (not shown) capable of housing therein a number of double-sided photosensitive films P each with a latent image formed thereon. In this case, double-sided photosensitive films P each with a latent image formed thereon are taken out of the cassette 10′ in a dark room or the like, and piled up in the magazine. The double-sided photosensitive films P1 thus piled up and housed in the magazine is also taken out one by one by the sucker 21.
Thus taken out, the double-sided photosensitive film P2 is conveyed toward the thermal development section 30 existing downstream in the conveyance direction, via the conveyor unit that has the conveyor roller pair 22 and the conveyor guide 23. Between the conveyor roller pair 22 and the thermal development section 30, there may be provided a positioning unit of correctly positioning the taken-out double-sided photosensitive film P2 in the direction perpendicular to the conveyance direction thereof to thereby correctly control the position of the double-sided photosensitive film P3 in the thermal development section 30 that is downstream of the apparatus.
In the thermal development section 30, there are provided the first heating unit 31 for heating the first face of the double-sided photosensitive film P3 and the second heating unit for heating the back thereof, in such a manner that they sandwich the conveyance route of the double-sided photosensitive film P3 between them. In this, the first heating unit 31 is provided with a number of heat rollers 31 each having a built-in heater in the center thereof; and the second heating unit 35 is a curved plate heater with a built-in surface heater 35 therein. As illustrated, nine heat rollers 31 are disposed at regular intervals along the inner face of the curved plate heater 35. These nine heat rollers 31 are driven to rotate in the clockwise direction by a common driving disc (not shown) at their edges.
Accordingly, the double-sided photosensitive film P3 having been conveyed to the inlet of the thermal development section 30 is led into the conveyance route formed by the distance between the first heating unit 31 and the second heating unit 35, and conveyed through them while its first face is heated by the heat rollers 31 and the opposite face is heated with the curved plate heater 35.
After both faces of the double-sided photosensitive film P3 has been uniformly heated in the thermal development section 30 in that manner as above, the film is then led to the pre-cooling section 40 disposed downstream in the conveyance direction. The pre-cooling section 40 is provided with a number of cooling roller pairs 41, in which the thermally-developed double-sided photosensitive film P4 is gradually cooled so that it is not wrinkled.
Thus gradually cooled in the pre-cooling section 40, the double-sided photosensitive film P5 is further cooled with the metal plates in the cooling section 50 so that it does not cause skin burns. The double-sided photosensitive film P thus finally cooled so that it gives not hot feel is further led downstream of the conveyance direction by the conveyor unit 60 that is provided with the take-out roller pairs 61 and 63 and the conveyor guide 63, and then taken out in the tray 70.
Since both the face and the back of the double-sided photosensitive film are subjected to simultaneous thermal development in the manner as above, there occurs no temperature difference between the two faces of the film, and therefore the double-sided photosensitive film can be developed uniformly with neither discoloration nor density fluctuation of the image formed thereon.
However, we the present inventors have found that, when the thermal development apparatus as described in FIG. 7 is used, then the image density is delicately unstable in that the image formed may be thick in some cases while it may be thin in some other cases. Having investigated the reasons for it, we have found that the moisture data in the apparatus are not reflected on the thermal development temperature therein.
On the other hand, the imager as described in FIG. 6 is free from the density instability of the images formed. The reason is because, in the imager of FIG. 6, films are set in the tray and their moisture content is relatively stable in one and the same pack.
As opposed to this, in the apparatus of FIG. 7, one double-sided photosensitive film is set in one cassette and brought out to various positions and the film in the cassette is imagewise exposed and developed in different environments. Accordingly, the double-sided photosensitive film is influenced by the humidity of the environment in which it is put, and the moisture content of the film therefore changes in different environments. Accordingly, since the heat of moisture vaporization from the films varies and it has some influence on the thermal development efficiency and, as a result, the image density becomes unstable.